A backlight is used to provide incident light for the liquid crystal display panel of a liquid crystal display device. An edge-type backlight comprises a light guide plate and a light source. The light source is bar-shaped, and light emitted from the light source enters into the light guide plate from a side (i.e., light incidence side) of the light guide plate, exits from the top of the light guide plate after being reflected, and is then provided to the liquid crystal display panel.
In the existing backlight, LED light bar is mainly used as the light source. The LED light bar is formed by arranging a plurality of LED lights on a bar-shaped circuit board. As shown in FIG. 1, the LED light 91 is actually a point light source and there is a space between adjacent LED lights 91, thus, if optical distance is insufficient due to too short distance between the LED light bar 9 and the light guide plate 8, portions, corresponding to the LED lights 91, of the edge of the light guide plate 8 have higher brightness, whereas portions corresponding to the spaces between the LED lights 91 have lower brightness. That is, hot spot phenomenon may occur, which influences the display effect.